Hi. I am trying to install a new programmable thermostat from one that is not labeled. When I remove the outer cover, I see two (2) red wires, (2) black wires, one (1) white wire and one (1) tan-ish color. There is no green, yellow, blue, etc. I have replaced a few of these thermostats before, but they were all color coded. Please help me determine which wires from the older connects with the newer model wires. Thanks much! :confused:

Need more info. What are the terminal designations on the old t-stat? Don't disconnect anything yet...

I don't recognize terminals or what they are. (My bad :o) All I see are wires coming through one hole from the back of the thermostat. I haven't disconnected anything yet. I attached a photo. Hopefully it is clear enough for you to recognize the connections.

What kind of system?

It says Lenox, spelled with one 'n'.

Oops. It IS Lennox with two 'n'.

Complete and exact model of furnace
Complete and exact model of old thermostat

Post both

Furnace: Lennox HP18-411U-3P
T-stat: Lennox 72F1101

Furnace: Lennox HP18-411U-3P
T-stat: Lennox 72F1101


From what I can tell that unit is about a 1984 vintage heat pump. Bad news is that someone wired it with non color code wiring which you already new. I can provide you with a universal wiring change over diagram and you will have to identify every wire you remove with the terminal it came off so as to use this universal change over diagram to transpose the old designated wires to the new thermostat terminals. Other option is to sound out each wire and see exactly where it goes on the air handler to find out exactly what it is used for. The next option is to have a professional do a on site srevice call to replace the thermostat. Sorry but under these circumstances this is all I can do.


Look under lennox 16,18,19 series

Thanks a million for your help. I will have a professional install it just for safety.

That is a smart idea. This way if they burn up the new thermostat they will have to get you a new one.